1. Technical Field
The present invention relates to a power converter which provided with a filter circuit.
2. Related Art
For example, patent document JP-A-2006-180578 and JP-A-2005-110406 respectively discloses a power converter such as a DC-DC converter in which an input filter circuit and/or an output filter circuit are provided. In the converter, an input filter circuit portion (component) 90a, power conversion circuit portion 90b and an output filter circuit portion 90c are disposed on a circuit board 93 as shown in FIG. 12.
The power conversion circuit portion 90b is a portion which mainly functions as the power converter, and conducts voltage transformation and so on. Both the input-filter circuit portion 90a and the output-filter circuit component 90b reduce conduction noise which travels through wiring on the circuit board. For example the input-filter circuit component 90a reduces conduction noise which gets mixed with the power conversion circuit portion 90b from the outside of the power converter 9. The output-filter circuit portion 90c reduces conduction noise which is output from the power conversion circuit portion 90b by both filter circuit portion 90a and 90b, thereby the conduction noise from output voltage can be reduced.
However one or more electronic components within the power conversion circuit portion 90b radiate noise and then the radiation noise spreads in space S and may affect the filter circuit component 90a and 90b. Thus there is a problem that noise reduction effects by the filter circuit component 90a and 90b are lowered. In the prior art, as this countermeasures, the power converter 9 prevents the radiation noise from propagating into the filter circuit component 90a and 90b in such a manner that each of the input-filter circuit component 90a, the power conversion circuit portion 90b and the output-filter circuit component 90c were covered with respective shield case 92.
However the conventional power converter 9 has a problem that not only production costs rise due to increase of amount of parts or components and of the manpower for its assembly but also the size of the power converter 9 enlarges caused by the one or more shield case 92 which is unacceptable.
Hence, in the light of conditions set forth above, it is needed to provide such a power converter that production costs can be lowered and downsizing of the power converter can be done.